Our objective is to develop flow cytometry techniques that may be used to detect and diagnose bladder cancer cells in irrigation specimens and voided urine, based on the cytochemical and physical properties of those cells. To do this, nuclear and cellular features known to distinguish cancer and benign cells are converted to machine readable form by using fluorescent DNA probes as cytochemical stains, and quantitating the appropriate photometric properties per cell at rates of several hundred cells per second. At present, we can measure total DNA and RNA per cell, nuclear and cellular size, and differences in nuclear chromatin conformation. These have been sufficient to distinguish benign and malignant bladder epithelial cells in tissue culture. In addition, these parameters identify proliferating cells (lymphocytes) in GO, G1, S, G2 and mitosis, and can be used for studies of cell cycle kinetics, possibly eventually to study the effects of drug therapy.